In these days of expensive vehicle fuel it has become practical for a driver to shut off the engine of his or her vehicle whenever it must sit for a limited time without moving. It has been calculated that the amount of fuel needed to start a motor-vehicle internal-combustion engine is equal to the amount of fuel burnt by the engine while running for five seconds. Thus if the engine is going to be shut off for more than 30 seconds a meaningful saving in fuel can be obtained. It is possible to save fuel by shutting off the engine at long traffic lights, when caught in traffic, or when the vehicle is standing still for a brief time for whatever reason.
The problem with shutting off the engine is that the average motor vehicle is not set up to make this operation easy. Normally shutting off the engine also shuts off the headlights, radio and other electrical equipment of the vehicle. Even on vehicles provided with an accessory position on the ignition switch to allow the headlights and other electrical equipment to operate, it is normally necessary to turn the ignition switch to the full off position before turning it into this accessory position, so that at the very least these electrical devices will be temporarily turned off. Furthermore the only method of shutting off the engine on most vehicles is by means of the ignition key which is also coupled to the steering lock. As a result even though substantial fuel savings could be realized, it is too inconvenient for the average driver to shut off the engine when this is possible and advisable.
It has been suggested in U.S. Pat. No. 4,006,723 to provide a system wherein the engine of the motor vehicle can be started after turning on the ignition and operation of a stop switch. The problem of such arrangement is that it is possible for the vehicle to be sitting still with its engine turned off merely by the stop switch so that inadvertent actuation of the starter switch, which can be integrated into the accelerator pedal, will start the engine. This can obviously lead to an accident. Furthermore the standard stop switch allows the engine to be stopped even on hills where the loss of pressure in power brakes or power steering could lead to a serious accident.